JPH0791049B2 - Polymer trichlorosilane conversion method in the production of polycrystalline silicon. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention [relates] is, SiHC ₃ Borima the SiHCl ₃ by-produced during the production of polycrystalline silicon (trichlorosilane) as a raw material
The present invention relates to a method of converting a polymer used in the production of trichlorosilane into trichlorosilane.

[Conventional technology]

Conventionally, polycrystalline silicon for semiconductor manufacturing comprises contacting a mixed gas of SiHCl ₃ and H ₂ on the silicon seed rods which are heated and maintained at about 1000 to 1100 ° C. in a bell jar furnace showing the SiHCl ₃ on the first equation It is produced by decomposing it into Si by a hydrogen reduction reaction and usually a thermal decomposition reaction shown in the second formula, and depositing Si on a silicon core rod.

SiHCl ₃ + H ₂ → Si + 3HCl (1) 4SiHCl ₃ → Si + 3SiCl ₄ + 2H (2) The mass balance at this time is industrially roughly as follows, although it depends on the reaction conditions.

That is, Si is generated from the gaseous SiHCl ₃ fed into the bell jar furnace, the remaining SiHCl ₃ is discharged, and Si
By-products such as H ₂ Cl ₂ , SiCl ₄ and polymers are produced and discharged.

Of the substances discharged from the bell jar furnace, the remaining SiHCl ₃
And by-products are liquefied and recovered, then distilled to obtain SiHCl ₃ ,
SiH ₂ Cl ₂ is separated. Separated SiHCl ₃ and SiH ₂ Cl ₂
Recycled for Si deposition reaction. The remaining fraction consisting of SiCl ₄ and the polymer is further distilled to be separated into SiCl ₄ and the polymer.

The polymer separated from SiCl ₄ consists of Si, H, and Cl, but the composition is not fixed.

Since this polymer is a substance that easily ignites in the air and is difficult to handle, it is conventionally hydrolyzed in an inert gas such as N ₂ gas, and at this time it is formed into a gel containing HCl and H _2. It is customary to further neutralize the substance with alkali to render it harmless.

[Problems to be solved by the invention]

However, the equipment and the treatment cost required for the detoxification treatment of the polymer are considerably large, which causes an increase in the production cost of polycrystalline silicon.

The present invention, when producing polycrystalline silicon from SiHCl ₃ ,
By utilizing the polymer produced as a by-product as a raw material for producing SiHCl ₃ , the raw material cost of polycrystalline silicon is reduced, and at the same time, the detoxification processing equipment and processing cost of the polymer are unnecessary, and the production cost of polycrystalline silicon is greatly reduced. It is intended to provide a method of converting a polymer to chlorosilane.

[Means for solving problems]

The present inventors have obtained the following findings as a result of investigating and handling the handling of a by-produced polymer when producing Si by reducing SiHCl ₃ with H ₂ .

When the polymer is heated at about 200 ° C. in an inert gas, most of it is separated into SiHCl ₃ and SiCl ₄ , and the rest becomes an oily substance. When the remaining oily substance is further heated to 300 ° C or higher, SiC
It was found that the substance decomposed into l ₄ , Si ₂ Cl _6, etc., and finally a reddish brown solid mainly composed of fine Si powder remained.

That is, the polymer is thermally decomposed into SiHCl ₃ , SiCl ₄ , and Si.
And so on.

On the other hand, when SiHCl ₃ is reduced with H ₂ to produce polycrystalline silicon, SiH ₂ Cl ₂ and SiCl ₄ are used in addition to the polymer as described above.
And so on. Of these, SiCl ₄ is mainly used as a raw material for the production of finely divided silica after being separated from the polymer, but it should be converted to trichlorosilane by the reaction with hydrogen and metallic silicon and reused as a raw material for the production of polycrystalline silicon. Is also possible.

In other words, the production of trichlorosilane can be achieved by using a packed bed of powder Si
HCl gas is blown in, and it is carried out in a state where powdered Si floats and flows by the gas. And this fluidized bed reaction is usually 300
The thermal decomposition of the polymer can be expected due to the fact that it is performed at around ℃, and since there is no oxygen in the fluidized bed, there is no risk of ignition of the polymer.

Based on the above, the present inventors
It was found that when injected directly into a fluidized bed for producing HCl ₃ , the polymer did not ignite, and the polymer can be safely used as a raw material for producing SiHCl ₃ .

The present invention has been made based on such findings, the SiHCl ₃
By-produced when producing polycrystalline silicon by reduction with H ₂
Si, Cl, and fed a Borima consisting of H into the reactor for the SiHCl ₃ production, and the gist of trichlorosilane conversion method of a polymer in the production of polycrystalline silicon, characterized by using as a raw material for producing SiHCl ₃ To do.

[Action]

SiHCl ₃ fed polymer in the fluidized bed for the manufacture is now pyrolyzed divided into SiHCl _3, SiCl _4, Si or the like, SiHCl ₃
To generate. In addition, SiCl ₄ , Si, etc., together with other feed materials,
Contributes to the production of iHCl ₃ .

〔Example〕

A typical example of the embodiment of the present invention will be described with reference to FIG.

Trichlorosilane can be produced by a transformation reaction using a mixed gas of metallic silicon, SiCl ₄ and H ₂ in addition to the above reaction of metallic silicon and hydrogen chloride.

SiCl ₄ is sent in a liquid state to the evaporator 1 together with H ₂ gas, heated to 150 ° C., vaporized, and sent to the fluidized reactor 2.

The fluidized reaction vessel 2 includes a dispersion plate 3 and a heater 4, and an industrial silicon 5 having a particle size of about 50 to 500 μm is provided on the dispersion plate 3.
Is filled.

The mixed gas of SiCl ₄ and H ₂ sent to the fluidized reaction vessel 2 flows into the Si packed bed from the bottom through the dispersion plate 3 and is heated to 500 to 600 ° C. by the heater 4 and flows into the Si packed bed from the bottom. The mixed gas thus formed becomes bubbles and rises in the Si filling layer 5,
The Si powder is allowed to flow in a floating manner, and SiHCl ₃ is produced by the reaction shown in the third formula during this period.

3SiCl ₄ + Si + 2H ₂ → 4SiHCl ₃ (3) The polymer generated together with SiCl ₄ during the production of polycrystalline silicon is pressurized by the pump 6 and charged into the fluidized bed from the bottom of the bed. The polymer fed into the fluidized bed is heated to 500 to 600 ° C., which is the ambient temperature in the bed, and is heated to SiHCl ₃ , SiC.
Decomposes into l ₄ , Si.

Of these, SiHCl ₃ rises in the fluidized bed as it is, and SiCl ₄ and Si produce SiHCl ₃ by the reaction shown in the third formula while rising in the fluidized bed.

The produced SiHCl ₃ is discharged to the outside from the upper part of the fluid reaction vessel 2, condensed and distilled, and then used as a raw material for producing polycrystalline silicon.

70 to produce 1 ton of polycrystalline silicon for semiconductor manufacturing
~ 100 kg of polymer was produced, which was conventionally detoxified and discarded, but in the present invention, the Si content in this polymer is
It is converted to SiHCl ₃ and further to polycrystalline silicon, so that detoxification treatment is unnecessary.

〔The invention's effect〕

As is clear from the above description, the present invention converts the polymer by-produced during the production of polycrystalline silicon into SiHCl ₃ ,
Furthermore, since it can be converted into polycrystalline silicon through SiHCl ₃ , the polycrystalline silicon manufacturing raw material can be effectively used, and the detoxification treatment of the polymer, which has been conventionally required, becomes unnecessary. It significantly reduces the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating an embodiment of the present invention. In the figure, 1: evaporator, 2: fluid reaction vessel, 3: dispersion plate, 4: heater, 5: silicon (fluidized bed).

Claims (1)

[Claims] Claim: What is claimed is: 1. When a SiCl ₃ is reduced with H ₂ to produce polycrystalline silicon, a by-product of a polymer of Si, Cl and H is converted into Si.
A method for converting a polymer into trichlorosilane in the production of polycrystalline silicon, which comprises feeding into a reaction furnace for producing HCl ₃ and using it as a raw material for producing SiHCl ₃ .